The statements made herein merely provide information related to the present disclosure and may not constitute prior art, and may describe some embodiments illustrating the present disclosure. All references discussed herein, including patent and non-patent literatures, are incorporated by reference into the current application.
At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the composition used/disclosed herein can also comprise some components other than those cited. In the summary and this detailed description, each numerical value should be read once as modified by the term “about” (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the summary and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any and every concentration within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to only a few specific, it is to be understood that inventors appreciate and understand that any and all data points within the range are to be considered to have been specified, and that inventors possessed knowledge of the entire range and all points within the range.
In oilfield operations involving coiled tubing, there is a fundamental limitation to the length of horizontal well that can be entered by the coiled tubing. This is primarily due to the friction between the coiled tubing and the wellbore. This friction produces an axial force in the coiled tubing directed against the motion of the coiled tubing, which, in turn, may eventually cause the coiled tubing to form into a sine wave and then a helix inside the wellbore. Once this has happened, any axial force applied from the surface produces a radial force that increases the frictional force resisting the motion of the coiled tubing into the hole. At some point during travel, the coiled tubing stops moving and begins to lock up, as will be appreciated by those skilled in the art. Conventional methods that have been applied to this problem include straightening the coiled tubing to cause it to resist starting to helix, using thicker and stiffer coiled tubing at the vulnerable section (instead of the usual taper where the thinnest wall is at the bottom), and using friction reducing compounds in the pumped fluid. Unconventional solutions include coiled tubing tractors, pumping glass beads, and downhole vibrators. Such vibrators act to produce small relative motions between the coiled tubing and the wellbore in the hopes of reducing the coefficient of friction and/or change it from static to dynamic friction.
However, there remains a need to further improve the system and method for reducing friction between coiled tubing and a wellbore penetrating subterranean formation.